This invention relates to radiation control sheet materials adapted to window and other solar applications. More particularly, it relates to radiation control sheet materials transmissive of visible light and selectively reflective of infrared radiation.
Various window-pane and like articles exhibiting visible light transmission and infrared (heat) reflecting properties have been described; and examples of such articles can be found in U.S. Pat. Nos. 3,781,077 (issued Dec. 25, 1973 to R. Groth); U.S. Pat. No. 3,849,244 (issued Nov. 19, 1974 to R. Groth); and U.S. Pat. No. 3,308,004 (issued Mar. 7, 1967 to P. Rouault). Typically, such articles will include a transparent support carrying a metallic or metalloid or semiconductive heat-reflective layer transmissive of visible and other solar radiation and reflective of infrared (heat) radiation. In addition to a heat-reflective layer, such an article may be provided with one or more layers of highly refractive dielectric material or polymeric or other protective layers for abrasion and corrosion resistance. The application of such additional layers presents certain requirements tending to make the production of such articles more costly or difficult to fabricate and in some cases resulting in radiation control sheet materials of reduced efficiency.
The application to a heat-reflecting layer of, for example, a low-reflection magnesium fluoride protective layer, requires the use of substantial heating for development of suitable hardness and durability. This requirement dictates the use of a glass substrate capable of withstanding the required heating and effectively negates the use of less costly and otherwise suitable plastic sheet materials. The application of a polymeric material as a protective layer may also be attendant with certain difficulties related to the manufacture or use of the desired radiation-control sheet material. For example, the polymeric protective layer may be inadequately bonded, such that handling during manufacture or use of the desired article may result in delamination or separation of the polymeric protective layer or other defects attributable to adhesion failure.